The present invention relates to map display technology, especially to three-dimensional map display method which is useful for applying to a navigation apparatus for displaying roads and buildings around the driving vehicle and near the cross way as three-dimensional images in a perspective map viewed in a designated angle with respect to the ground surface.
In the present invention, the term designated as structure represents structural objects, buildings, road and railways comprising the map. The term designated as decomposition structure represents a single structure existing on the plural mesh regions defined in the map data base and formed as a set of decomposed units each corresponding to the individual mesh regions, and the term designated as non-decomposition structure represents a single structure located and bound within a single mesh region.
Such a navigation apparatus is well known as an apparatus which supports the driver by displaying maps containing buildings and roads on a display screen by reading the digital map data stored on a memory device such as CD-ROM and DVC, and displaying the present position of the driving vehicle detected by the position detection sensor and the navigation guidance to the driver's designation location on the map.
In the recent map data in which street maps are stored, the detail information such as shapes, positions and the number of floors of residential houses and buildings can be displayed on the navigation apparatus. In addition, there is such an apparatus as using a method for displaying the buildings for providing landmark information in a three-dimensional view in the detail map information in order to present maps around the driving vehicle, the destination location and the cross way to be visited along the driving visually in more familiar manner.
The map data store the map information containing roads and buildings as decomposed meshes with designated intervals for the latitude and the longitude. As, in this kind of map data, the map information regarding the roads and buildings existing on the mesh boundaries is stored as plural sets of information decomposed by the mesh boundaries, there is such a problem that mesh boundary lines are displayed and super positioned on the structures such as residential houses and buildings existing on the mesh boundaries in the conventional method in which the map is displayed by reading the map data mesh by mesh.
As, In case of mapping textures such as windows on the side wall of the decomposed structure, the mapped textures are displayed discontinuously at the mesh boundaries, the mesh boundaries are displayed more explicitly than the case of displaying the map in a two-dimensional view, which results in the unexpected image for the user attempting to recognize the actual structures, and even leads to such a problem that the primitive objective for presenting the informative navigation guidance map in a familiar manner with three-dimensional view may not be attained.